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Handy Hints: How to detect and deal with LDAs

A left displaced abomasum can be a sign a herd’s transition period needs attention. Louise Hartley talks to vet Matt Hylands of Lambert Leonard and May Farm Veterinary Surgeons about the disease.

A left displaced abomasum (LDA) is a costly condition, not only due to the drug and vet fees, but also the reduced milk yield and subsequent effect on fertility.

In theory, it can occur in any cow in any herd, but in practice, it is a disease of high-yielding dairy cows in early lactation.

Matt Hylands, from the Lancashire branch of Lambert Leonard and May, explains the condition.

What is an LDA?

The abomasum is the cow’s fourth, or true, stomach. It is the final stomach on the diet’s journey to the intestines and, like our stomach, is where a lot of chemical digestion takes place.

It lies on the floor of the abdomen on the right-hand side, just behind the lungs and diaphragm.

A displaced abomasum is seen when the abomasum moves from its normal anatomical position. An LDA occurs when the abomasum drifts over to the left of the cow and lies between the rumen and the left body wall [see below]. It constricts outflow, causing a build-up of gas and a dilated abomasum.

Why does the condition occur?

The exact cause is still not thoroughly understood. It is thought during pregnancy the uterus pushes the abomasum slightly to the left, which ordinarily will return to its normal position on the right immediately after calving, presumably helped by the massive rumen which naturally lies on the cow’s left-hand side.

It is well-documented a cow’s dry matter intake around calving naturally drops, meaning the rumen takes up a fraction of the space it originally did, resulting in less pressure on the abomasum to return to the right-hand side.

In addition, after calving, the abomasum can develop atony [a lack of tone], which means its contents fail to pass through, and instead gas builds up, making the chance of it drifting between the rumen and left body wall even more of a risk.

Factors

A number of different factors cause abomasal atony, including acidosis, ketosis, hypocalcaemia [milk fever], mastitis or metritis.

All these conditions are commonly encountered at or around calving and usually cause a further drop in dry matter intake, meaning an even smaller rumen and even bigger risk of a displacement.

Although LDAs make up 80-90 per cent of displaced abomasum cases, cows can also suffer from right displaced abomasums, caused by the same principles.

What are the clinical signs of an LDA?

The most common symptom of an LDA is unsatisfactory milk yield in the cow’s first month in-milk. She may also have a loss of appetite, quite often eating forage but refusing concentrates.

Unless the abomasum is significantly bloated, or an ulcer is present, the heart rate and vital signs tend to be within normal limits.

Can I diagnose it? How do I do it?

Yes. Tapping the skin with your fingers while listening with a stethoscope along a diagonal line drawn between the cow’s left hip and elbow will reveal an area of high-pitched pinging, usually over the last rib, similar to a drop of water falling into a tin bucket [see diagram below].

Practice makes perfect, and once heard, this sound is very hard to miss.

Can it be prevented?

Prevention is better and cheaper than cure. It is based around minimising the natural fall in dry matter intake at calving and preventing any abomasal atony.

Maintaining a true, well-run transition cow group with a specific transition diet minimises the drop in dry matter intake at calving, hence maintaining rumen size within the abdomen.

Cows fed a proper transition diet are also less likely to suffer from milk fever or ketosis and so abomasal atony is much less likely to occur.

Cows with elevated ketones post-calving are up to eight times more susceptible to LDAs.

Risk

Ensuring cows are not over- or under-fat, with a body condition score of 2.5-3.5, throughout the dry period, reduces risk of an LDA.

Fat cows have a bigger drop in dry matter intake at calving, meaning relatively smaller rumens, but also mobilise fats into the bloodstream, which can cause abomasal atony and suppress the immune system, opening the door for post-calving disease.

Any post-calving disease, including metritis, mastitis or retained foetal membranes, must be diagnosed and treated immediately to prevent dropping dry matter intakes or abomasal atony.

Cows suffering from LDAs will most likely only represent the tip of the iceberg. Acting to prevent future cases via a thorough review of transition management will not only decrease cases of LDAs, but will increase herd health and productivity too.